Journal of Advanced Research Design
ISSN (online): 2289-7984 | Vol. 10, No.1. Pages 9-13, 2015
9
Penerbit
Akademia Baru
The Effect of Poly (ethylene glycol) Diglycidyl
Ether as Surface Modifier on Conductivity and
Morphology of Carbon Black-Filled Poly (vinyl
chloride)/Poly (ethylene oxide) Conductive
Polymer Films
M. D. Siti Hajar*,1,a, A. G. Supri2, b and A. J. Jalilah3,c
1,3School of Materials Engineering, Universiti Malaysia Perlis (UniMAP), Kompleks Taman
Muhibah, Jejawi 2, Perlis, Malaysia 2 Faculty of Engineering Technology, Universiti Malaysia Perlis (UniMAP), Pauh Putra,
Arau, Perlis *,[email protected], [email protected], [email protected]
Abstract – Blends of poly (vinyl chloride) and poly (ethylene oxide) with the addition of carbon black
as filler was prepared via solution casting technique to fabricate a conductive polymer film. Besides,
poly (ethylene glycol diglycidyl ether) (PEGDE) was added into the formulation in order to improve its
properties. The surface morphology of the conductive polymer film was characterized via scanning
electron microscope (SEM). The results showed that the conductivity of the film was greatly enhanced
by incorporating the PEGDE as the surface modifier in the PVC/PEO conductive polymer film.
Copyright © 2015 Penerbit Akademia Baru - All rights reserved.
Keywords: Poly (vinyl chloride), Poly (ethylene oxide), Poly (ethylene glycol) Diglycidyl Ether, Electrical
conductivity
1.0 INTRODUCTION
Polymer blending is one of the most important methods for the development of new materials
with a variety of properties and superior than the individual component polymer. It is one of
the efficient ways to reduce the crystalline content, as well as to improve the amorphous
content. Generally, the polymer materials are insulators and they blend with conductive filler
to improve its conductivity properties. The conductivity of the composite materials depends on
the size and the shape of the filler particles, in addition to their distribution within the polymer
matrix [1]. The conductivity of the polymer increases if the added filler forms a continuous
conductive network in the matrix. Some examples of conductive fillers, in order to form a
conductive network, are natural and synthetic graphite, copper, carbon black, and carbon
nanotubes [2].
Polyvinyl chloride had been chosen as the polymer matrix because of its broad range of
application, low in cost, chemical stability, biocompatibility, and sterilizability. Besides, it has
Journal of Advanced Research Design
ISSN (online): 2289-7984 | Vol. 10, No.1. Pages 9-13, 2015
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Penerbit
Akademia Baru
been broadly used in the industry for many years. However, PVC has low thermal stability and
brittleness, which hinders certain applications. Therefore, it is important to blend PVC with
other polymer materials to achieve good properties in order to yield high added values [3].
Polyethylene oxide (PEO) is a semi-crystalline polymer, owning both crystalline and
amorphous phases at room temperature. It is the most interesting base material because of its
high thermal property and chemical stability [1, 4]. On top of that, PEO is a weak proton
acceptor polymer, and therefore, it is compatible with PVC because PVC can be considered as
a proton donor that contributes acidic hydrogen. In recent years, PVC has been commonly used
in polymer blending due to its miscibility with other polymer materials.
On the other hand, carbon black (CB), which is commonly used in the industry to achieve
conductive polymer composites due to its cost advantage over many other types of fillers and
abundant supply, exhibits the particle shape at relatively low concentration, as well as
supermolecular structures at relatively high concentration [5]. Besides, CB has been widely
used as conductive filler in order to transform the insulating nature of polymers to electrically
conductive due to its easy process ability and light weight compared to other metallic particles
[6]. Meanwhile, poly (ethylene glycol diglycidylether) (PEGDE) is also commonly used in the
chemical industry for surface modifying and crosslinking. It has widely acted as an additive
for crosslinking polymers bearing amine, hydroxyl, and carboxyl groups, besides possessing
good solubility in water [7]. In polymer electrolyte application, PEGDE is usually incorporated
as a plasticizer and stabilizer. It does not only improve the conductivity, but also the high
chemical stability of the solid polymer electrolyte. Recently, Jing Fu et al. reported that the
measured conductivity of the alkaline solid polymer electrolyte membrane from PVA ranged
from 2.75 to 4.73 x 10-4 Scm-1 at room temperature increased up to 1.5 x 10-3 Scm-1 with
addition of PEGDE. This was due to the high chemical stability of the membranes that was
achieved by high densely chemical crosslinking modification, as well as the formed inter-
penetrating network of the membrane [8].
In addition, the important objective of the research was to study the effect of PEGDE and the
loading of the conductive filler on the properties of PVC/PEO films. Therefore, this research
reports an investigation on electrical conductivity properties, as well as morphology of
PVC/PEO-filled CB conductive film by varying CB loading and adding PEGDE in the
conductive polymer film.
2.0 METHODOLOGY
2.1 Materials
Poly vinyl chloride (PVC) with M.W ≈ 220 000 and poly ethylene oxide (PEO) with M.W ≈
100 000 were used as the basic polymeric matrix. Carbon black (CB) with the mean particle
sized < 177 µm was used as conductive filler in the conductive polymer blend. Besides,
dioctylterepthalate (DOTP) with M.W ≈ 390.56 was used as a plasticizer.
2.2 Sample Preparation
The PVC and the PEO conductive films were prepared by using the solution cast technique.
The required amounts of PVC and PEO were dissolved in Tetrahydrofuran (THF) with a stirrer
at a speed of 600 rpm. The solution was prepared at room temperature. After incorporating the
required amount of Dioctylterepthalate (DOTP) as plasticizer, PEGDE as surface modifier, and
CB was suspended in the PVC/PEO blends. The mixture was stirred continuously for 4 hours
Journal of Advanced Research Design
ISSN (online): 2289-7984 | Vol. 10, No.1. Pages 9-13, 2015
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Akademia Baru
until a homogeneous mixture was obtained. Then, the mixture was cast onto a glass mould and
was allowed to evaporate slowly inside a fume cupboard at room temperature. The same
methods were repeated to produce samples with different CB loading.
3.0 RESULTS AND DISCUSSION
Figure 1 shows the relationship of the electrical conductivity as a function of the conductive
filler content for PVC/PEO/CB films and PVC/PEO/CB/PEGDE films. From Fig. 1, the
electrical conductivity of the PVC/PEO conductive film increased with the increase of CB
loading. The increment of electrical conductivity was due to the increase of surface interaction
between CB particles in PVC/PEO/CB films. However, the PVC/PEO/CB/PEGDE films
showed higher electrical conductivity compared to PVC/PEO/CB films. This was because the
addition of PEGDE enhanced good distribution of CB on the surface of the PVC/PEO/CB
films. The presence of PEGDE also promoted proton conduction and increased the conductivity
value. Meanwhile, Jin et al. studied the effect of PEGDE content as plasticizers on the ionic
conductivity of (PEO-PMA)-based polymeric gel. The results showed that the ionic
conductivity increased with the increase in the content of PEGDE [9].
Meanwhile, the percolation threshold value was about 20wt% for both PVC/PEO/CB films and
PVC/PEO/CB/PEGDE films. A percolation threshold in conductivity is present when the
volume fraction of the filler is enough to provide continuous electrical paths through the
polymer matrix. Besides, the percolation threshold is varied with shapes and agglomeration of
the filler, as well as the type of polymer used [10].
Figure 1: Electrical conductivity of PVC/PEO/CB films and PVC/PEO/CB/PEGDE films
with different CB loading.
Figure 2(a-c) show SEM micrographs of extracted surface for PVC/PEO blended with CB
loading. From the micrograph, at 5 wt% of CB loading, there was a good distribution of CB in
the PVC/PEO blends, indicating a good interaction between CB and PVC/PEO phases.
Nevertheless, when the content of CB was increased to 30 wt% (see Fig. 1(c)), the CB particles
in the PVC/PEO blends formed an agglomeration on the surface of the film. The
1.00E-10
1.00E-09
1.00E-08
1.00E-07
1.00E-06
1.00E-05
1.00E-04
1.00E-03
1.00E-02
1.00E-01
1.00E+00
5 10 15 20 25 30
Ele
ctri
cal
Co
nd
uct
ivit
y,
(S/c
m)
Carbon Black Loading, (wt%)
CB CB/PEGDE
Journal of Advanced Research Design
ISSN (online): 2289-7984 | Vol. 10, No.1. Pages 9-13, 2015
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Penerbit
Akademia Baru
agglomerations of CB particles that were formed on the surface paved the connection of the
conductive path on PVC/PEO/CB conductive films that contributed to higher conductivity
value when compared to 5 wt% of CB loading.
In addition, Figure 2 (d-f) show images of SEM micrographs for extracted surface of PVC/PEO
blends with different CB loading and the addition of PEGDE as surface modifier in the
conductive polymer films. However, the PVC/PEO/CB/PEGDE films showed many holes on
the extracted surface compared to PVC/PEO/CB films. Furthermore, the surface was found
rougher when the CB content was increased by 5 wt% to 30 wt%. This was due to the extraction
of PEGDE during the immersion of the films in toluene for 24 hours.
(a) 5 wt% CB (b) 15 wt% CB (c) 30 wt%CB
(d) 5 wt%
CB/PEGDE
(e) 15 wt%
CB/PEGDE
(f) 30 wt%
CB/PEGDE
Figure 2: SEM micrographs of extracted surface of PVC/PEO/CB and
PVC/PEO/CB/PEGDE conductive polymer films.
4.0 CONCLUSION
The PVC/PEO/CB conductive polymer films were produced by using solution casting method.
In fact, some improvements were made by incorporating PEGDE as the surface modifier.
Besides, the electrical conductivity of the PVC/PEO polymer films increased with the addition
of PEGDE as surface modifier into the PVC/PEO/CB films.
Journal of Advanced Research Design
ISSN (online): 2289-7984 | Vol. 10, No.1. Pages 9-13, 2015
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